1. Field of the Invention
The present invention relates to a device for filtering out rotational vibrations, for filtering out vibrations transmitted by a rotary power component adapted to drive an output shaft in rotation; the said rotary power component is for example the crankshaft of a motor vehicle heat engine.
2. Description of the Prior Art
Devices are known for filtering out rotational vibrations, that consist of a mass which is elastically coupled on the shaft: such devices, known as passive dampers, work very well in filtering out vibrations tuned to a single frequency which is clearly determined, but for neighbouring frequencies, the vibrations are, by contrast, amplified.
So-called active drive shaft dampers have been proposed, as for example in the document FR-A-2 658 888, the construction of which is similar to that of an electric motor; it is so controlled that the torque which it supplies works in opposition to the vibration to be filtered out, over a given range of rotation: the electrical power consumption of such devices is not insignificant.
An object of the invention is to overcome these drawbacks.